Sonic mosquito repellents 'don't work'Trials find no evidence devices are effective

18 April 2007

 

Mosquito

Mosquitoes: small but potentially deadly

Electronic mosquito repellents that are supposed to drive the insects away with high-pitched sounds do not work, researchers said today.

A review of ten field trials in various parts of the world provided no evidence that the devices were effective.

Yet their manufacturers claim they can help prevent people catching malaria from mosquito bites.

The disease affects more than 250 million people worldwide and causes more than a million deaths each year.

High frequency buzz

Electronic mosquito repellents (EMRs) are battery-powered hand-held devices that emit a high frequency buzz almost inaudible to the human ear.

They are claimed to repel mosquitoes within a range of up to 2.5 metres, both indoors and outdoors.

Mobile phone companies also market a ring tone that is said to deter mosquitoes.

The gadgets target female mosquitoes, because only they bite. It is claimed they mimic the flight sound of males, and this may repel the female insects once they have mated.

Malaria infection

Another explanation is that they sound like bats, which prey on mosquitoes.

The scientists, led by Dr Ahmadali Enayati, from the Mazandaran University of Medical Sciences in Iran, analysed data from 10 trials which assessed the number of mosquitoes landing on the bodies of human volunteers.

‘All 10 studies found that there was no difference in the number of mosquitoes found on the bare body parts of the human participants with or without an EMR,’ said Dr Enayati.

The paper was published by the Cochrane Library, part of the Cochrane Collaboration, a UK-registered charity which specialises in research reviews.

The scientist wrote: ‘EMRs have no effect on preventing mosquito bites. Therefore there is no justification for marketing them to prevent malaria infection.’

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